What makes foggy weather

Sometimes it is cold enough, but the air does not have any particles. When it comes into contact with cold surfaces such as roads and sidewalks, it instantly forms a dangerous icy layer.

The smoke provides particles for the water vapor to condense around. This combination of smoke and water vapor is a dangerous one. A super fog is so dense that you would not be able to see your own hand in front of your face. Superfogs create very hazardous driving conditions. Fog and smoke from a brush fire combined to make a super fog, resulting in this massive car accident in Florida in Photo used with permission of Orlando Sentinel, Copyright Thousands of driving accidents happen each year because of fog.

Or, as is more often the case, infrared cooling of a cloud-free, humid air mass at night can lead to fog formation - this is called "radiation fog". Radiation fog is most common in the fall, when nights get longer, airmasses begin to cool, and land and water surfaces that have warmed up during the summer are still evaporating alot of water into the atmosphere.

Finally, a warm moist air mass blowing over a cold surface usually snow or ice, or over a cold ocean surface can also cause fog to form-this is called "advection fog".

The fog droplets forming at the snow surface release the latent heat of condensation, which helps to melt the snow. As the air cools during the longer night the relative humidity increases, which can result in to fog formation. Windy mornings are fog free as strong winds mix the air near the ground with the drier, warmer air above. As autumn progresses, we will see a fog during the day forming over the unfrozen lakes.

This fog, called evaporation fog, forms when colder air moves over warmer water. Evaporation fog over a lake gives the appearance of steam rising out of the water and is sometimes referred to as a steam fog. Fogs which are mainly composed of water droplets are generally classified according to the physical process which produces saturation or near-saturation of the air. Radiation fog usually occurs in the winter, aided by clear skies and calm conditions.

The cooling of land overnight by thermal radiation cools the air close to the surface. This reduces the ability of the air to hold moisture, allowing condensation and fog to occur. Radiation fog usually dissipates soon after sunrise as the ground warms. An exception to this can be in high elevation areas where the Sun has little influence in heating the surface.

Valley fog forms where cold dense air settles into the lower parts of a valley, condensing and forming fog. It is often the result of a temperature inversion , with warmer air passing above the valley. Valley fog is confined by local topography and can last for several days in calm conditions during the winter.